1. Field of the Invention
The present invention relates to an automatic steering system for a vehicle for automatically parking the vehicle without recourse to steering by a driver.
2. Description of the Prior Art
Automatic steering systems for vehicles are already known from Japanese Patent Application Laid-Open Nos. 3-74256 and 4-55168. These automatic steering systems for vehicles utilize an actuator for a conventional well-known electric power steering system, and are designed so that reverse parking or longitudinal parking is automatically performed by controlling the actuator based on a previously stored relationship (a standard locus of movement) between the traveling distance of the vehicle and the steering angle.
In the above conventional system, it is necessary to steer the wheel more rapidly, as the vehicle speed becomes higher. However, if the weight of a load on the vehicle is large, or if the road surface friction coefficient is high, a larger force is required for the steering. For this reason, if the performance of the actuator is low, the vehicle cannot be moved with a good accuracy on the standard locus of movement and as a result, the vehicle cannot correctly reach the target position, in some cases.